1. Field of the Invention
The present invention relates to a light coupling apparatus for use in an optical equipment. In particular, it relates to an apparatus for coupling a plurality of different incident lights from different light sources into lights in a substantial single outward direction or in a plurality of different outward directions.
2. Descriptions of the Related Art
In recent years, the market for optical equipment has developed significantly, improving the quality of related products as well. For example, related optical coupling apparatuses, such as an X-cube, and an X-plate, are widely used and have been dramatically improved. Still, providers are continuing to improve the quality of optical apparatuses to get better light coupling quality.
Taking a Liquid Crystal Display (LCD) as an example, the light projected by a light source must be divided into a red light, a blue light, and a green light by a dichroic mirror. The divided lights then need to be coupled by a light coupling apparatus (usually with an X-cube) to efficiently converge the lights. Finally, the light is incident to an imaging system and is in conjunction with imaging signals to generate an image. FIG. 1_(a) to FIG. 1_(d) includes several kinds of known light coupling apparatuses to schematically show the methods of light coupling.
FIG. 1_(a) shows the way of light coupling of a known X-cube made by four prisms. As shown, an incident light is divided into a red light (R) 101, a green light (G) 102, and a blue light (B) 103. These lights are then coupled by the X-cube 10 into a white light (W) 104. Different kinds of dichroic coatings are applied on a first interface 105 and a second interface 106. The dichroic coating on the first interface 105 allows the red light (R) 101 to reflect and the green light (G) 102 and the blue light (B) 103 to pass through the first interface 105. Likewise, the dichroic coating on the second interface 106 allows the blue light (B) 103 to reflect and the green light (G) 102 and the red light (R) 101 to pass through the second interface 106. After light coupling, a white light (W) 104 is generated. In addition, the light source for use with the X-cube must be divided into R, G, and B primary colors. The incident directions of the lights after division must be fixed as shown in FIG. 1_(a). If the incident directions are at different angles, either light coupling will fail or the white light will be of poor quality.
FIG. 1_(b) shows light coupling of a known X-plate. Comparing with the X-cube 10, the X-plate 20 is configured by two dichroic mirrors. Because the X-plate and X cube 10 share similar features, some reference numerals in FIG. 1_(b) and FIG. 1_(c) (mentioned later) will be the same as FIG. 1_(a). As shown in FIG. 1_(b), the incident light is divided into a red light (R) 101, a green light (G) 102, and a blue light (B) 103. These lights are then coupled by the X-plate 20 into a white light (W) 104. Different kinds of dichroic coatings are applied onto a first plate 105a and a second plate 106a. The dichroic coating on the first plate 105a allows the red light (R) 101 to reflect and the green light (G) 102 and the blue light (B) 103 to pass through the first plate 105a. The dichroic coating on the second plate 106a allows the blue light (B) 103 to reflect and the green light (G) 102 and the red light (R) 101 to pass through the second plate 106a. After light coupling, a white light (W) 104 is generated. The X-plate may be a simpler design in comparison with the X-cube; however, it bears disadvantages that the incident lights must be divided into different single colors beforehand, and the incident angles of light is inflexible. FIG. 1_(c) shows light coupling of known dichroic mirrors. Comparing with the X-cube 10 and the X-plate 20, the dichroic mirror assembly 30 is configured by two diachronic mirrors 107, 108 and a regular mirror 109. As shown in FIG. 1_(c), the incident light is divided into a red light (R) 101, a green light (G) 102, and a blue light (B) 103. The lights are then coupled by the dichroic mirror assembly 30 into a white light (W) 104. The dichroic coating applied on the first dichroic mirror 107 allows the red light (R) 101 to reflect and the green light (G) 102 and the blue light (B) 103 to pass through the first dichroic mirror 107. The other dichroic coating applied on the second dichroic mirror 108 allows the green light (G) 102 to reflect and the blue light (B) 103 to pass through the second dichroic mirror 108. Unfortunately, in this design, the lights must be divided beforehand. In addition, the incident angle can not be adjusted flexibly.
In addition to the aforementioned limits of the three known designs, it is difficult to couple more than three incident lights into a white light. In other words, the prior art is only for the application of coupling three divided lights into a white light.
Another known apparatus combining mirrors 40 is shown in FIG. 1_(d). The ends of the two mirrors 110 form an angle 111, allowing two incident lights 112 to reflect off the mirrors 110, and couple into a white light. Although this apparatus overcomes the need to divide the lights beforehand, it is still not flexible enough to couple more than two incident lights.
Thus, a coupling technique that resolves the previously mentioned limitations is needed in this field.